Voltage regulator and data path for a memory device

ABSTRACT

A method and apparatus provide unbalanced output drive capability, for example, to correct for output skews in subsequent output stages. In one aspect, a pre-driver or the like provides unbalanced output drive capability. The pre-driver is comprised of first and second data paths having a plurality of transistor output stages and a plurality of switches for controlling the conductivity of the plurality of output stages in response to the level of conductivity of a subsequent driver output stage. A method of correcting output skews in a subsequent amplification stage is also provided. In another aspect, a portion of a data path, a memory device, and a computer system all have a pre-driver with pre-driver output transistors responsive to signals indicative of the strength of output drive transistors.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation of U.S. application Ser. No.09/792,554 entitled “Voltage Regulator and Data Path for a MemoryDevice” filed 23 Feb. 2001, now abandoned, which is a divisional of U.S.application Ser. No. 09/654,099 entitled “Voltage Regulator and DataPath for a Memory Device” filed 31 Aug. 2000, issued as U.S. Pat. No.6,545,929.

BACKGROUND

The present invention is directed to memory devices generally and, moreparticularly, to voltage regulators and data paths used in such devices.

Solid state memory devices communicate with the outside world throughinput/output pads. Some pads may be connected to an address bus and arethus dedicated to receiving address information. Other pads may beconnected to a command bus from which command signals are received whilestill other pads are connected to a data bus, on which data to bewritten into the memory is received or data read from the memory isoutput. In other types of devices, the pads may be connected to a singlemultiplexed bus which, at one point in time outputs address and commandinformation and, at another point in time, outputs or receives data.

To enable pads to receive or send information, the information istransmitted in the form of ones and zeros. The “ones” and “zeros” aretypically represented by two different voltage levels. For example, avoltage between two and five and one half volts may be considered torepresent a high signal, or a “one”, while a voltage level of betweenminus 0.3 volts and plus 0.8 volts may be considered to represent a lowsignal, or a “zero”. The output pads must be capable of reliablyproducing voltages within the ranges designated as representing ones andzeroes in accordance with timing specifications set for the component.

Timing specifications are typically set by the consumers of the memorydevices for particular applications. A timing specification wouldidentify how long it may take for an output pad to change from a zero toa one, e.g. change from minus 0.3 volts to plus five volts, how abruptthe changes must be, etc. With access times for memory devices measuredin nanoseconds, it is clear the design engineer is faced with quite achallenge to design electrical circuits which can change the voltageavailable at the output pads so quickly.

Output pads typically are serviced by a number of circuits such ascircuits for buffering (holding) data, and drive circuits for drivingthe voltage on the pad to a voltage representative of data to be output.The drive circuit, in turn, is serviced by devices such as voltagegenerators and voltage regulators which provide the power needed by theoutput pad drivers. The voltage regulator is used to provide power, inthe form of voltage for driving the gate of an output transistorultimately servicing an output pad. Typically, voltage regulators supplythat gate voltage (Vgate) to a number of drive transistors through avoltage bus.

When the gate voltage is heavily loaded, the Vgate level recovery maynot be sufficiently quick. Prior art attempts at solving this problemapply a one-shot pulse to an enable Vgate line. However, because thepath between Vgate and the enable Vgate line is through a p-channeltransistor with its n-well biased to Vgate, there is a risk of forwardbiasing the drain of the p-channel to the n-well if the one-shot pullingthe enable V-gate line towards system voltage (V_(DD)) is not timedproperly across all process and device conditions. Additionally, if theone-shot timing is too weak under particular process and deviceconditions, then Vgate will droop, and the enable Vgate lines will notrecover sufficiently quickly.

Another problem is experienced in the prior art when the memory device,and hence the voltage regulator, must go into a nap or a standby mode.In such modes, the Vgate regulator needs to go to a low power mode veryquickly. In some prior art configurations, that is accomplished byreducing the bias voltage supplied to an amplifier within the voltageregulator. However, simply reducing the bias voltage may not reduce thepower consumption of the voltage regulator sufficiently quickly.

Another problem is encountered because output transistors typically havean RC time constant associated therewith as a result of their loading.The RC time constant prevents the output transistor from reducing itsdrive sufficiently quickly. In the prior art, a pass gate is used todisconnect the RC so that the output transistor can respond morequickly. However, that approach leaves one side of the RC load floating.Due to n-plus junctions, the floating side can move to a back biasvoltage. Should that occur, when the RC is reconnected to thetransistor, the transistor would be turned on hard.

Other problems associated with the data path relate to the output slewof data pad drivers. In the prior art, output slew rates are improved bysegmenting the output transistors into two main portions and delayingthe switching of one of the portions. The delay is controlled by acircuit that makes a determination as to the strength of the p- andn-channel transistors and generates a two-bit binary code. In additionto setting the delay based on the two-bit code, a NAND gate is used toreceive the two-bit signal which, in turn, enables a p-channeltransistor to further enable two other p-channel transistors in theoutput pre-driver so that they could strengthen the high side out of thepre-driver for both the normal and delayed paths. However, variouschanges over process and device conditions can cause the output's timingcharacteristic to be skewed. Because the prior art solution enables onlythe addition of p-channel transistors in one of the two-bit code cases,the degrees of freedom to compensate for various types of skew arelimited.

Thus, the need exists for a voltage regulator and data path withimproved performance characteristics.

SUMMARY

One aspect of the present invention is directed to a method andapparatus of boosting the gate voltages for transistors controlling thevoltage appearing on output pads of a solid state memory device, withthe gate voltages being supplied by a voltage regulator through anoutput bus. The demand for gate voltage is periodically determined and,when the demand is high, each line of the bus may be momentarilyconnected to a voltage source. In addition, additional current istemporarily sourced to the output terminal of the voltage regulator.

Another aspect of the present invention is directed to a method andapparatus of producing a control pulse of an extended duration for usein the voltage regulator having its output terminal connected to avoltage bus, and with the voltage bus serving a plurality of outputblocks through a plurality of output lines. A first logic gate receivesa plurality of signals each representative of the voltage demand of oneof the plurality of output blocks and produces a control pulse of afirst duration. A plurality of delay circuits receives the control pulseand produces a plurality of delayed control pulses. A second logic gatereceives the control pulse and the plurality of delayed control pulsesand produces a control pulse of extended duration. The control pulse ofextended duration may be used, for example, for temporarily sourcingadditional current to an output terminal of the voltage regulator.

According to another aspect of the present invention, a method isdisclosed of forcing a voltage regulator into a low power mode. Themethod involves increasing the rate at which a bias voltage is withdrawnfrom an amplifier in the voltage regulator. A node between a resistiveand capacitive load connected to an output transistor of the voltageregulator is pulled to a predetermined voltage other than ground. Byreducing the bias voltage, power consumption is rapidly diminished.Furthermore, by pulling the node to a predetermined voltage other thanground, the node is prevented from floating to a voltage which will turnthe transistor on hard when reconnected.

Another aspect of the present invention is directed to a pre-driver orthe like which provides variable output drive capability. The pre-driveris comprised of two paths each divided into output stages. A two-bitsignal is generated in response to determining the relative strength ofthe n-channel and p-channel transistors in a subsequent outputamplifier. The two-bit signal is then used to enable certain of theoutput stages in each of the output paths.

The present invention solves the problems encountered in prior artvoltage regulators used in memory devices or other types of demandingapplications. For example, the present invention insures that the powerprovided by the voltage regulator is adequate even under heavy loadconditions. The present invention insures that the power consumption isquickly reduced when the device is put into a nap or standby mode whileat the same time insuring that the device will properly power up whendesired. The present invention also improves the performance of the datapath. Those, and other advantages and benefits, will become apparentfrom the Description of the Preferred Embodiment hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

For the present invention to be easily understood and readily practiced,the present invention will now be described, for purposes ofillustration and not limitation, in conjunction with the followingfigures wherein:

FIG. 1 is a block diagram of a memory device illustrating a voltageregulator servicing a number of output blocks;

FIG. 2 is a circuit diagram of an output block of FIG. 1;

FIG. 3 is a circuit diagram illustrating one implementation of a voltageregulator constructed according to the teachings of the presentinvention;

FIG. 4 is a circuit diagram of control circuit used in conjunction withthe voltage regulator of FIG. 3;

FIG. 5 is a circuit diagram of a circuit for controlling the decrease inbias voltage supplied to the differential amplifier of FIG. 3;

FIG. 6 illustrates an implementation for the output transistors of adata pre-river or the like; and

FIG. 7 is a block diagram of a computer system in which the memorydevice of FIG. 1 may be used.

DESCRIPTION

The present invention will now be described in conjunction with FIG. 1which illustrates a memory device 10. The reader will understand thedescription of the present invention in conjunction with the memory 10of FIG. 1 is merely for purposes of providing one example of anapplication for the present invention. The present invention is not tobe limited to the application shown in FIG. 1.

The memory device 10, includes an array 12 of memory cells. The memorycells 12 are arranged in rows and columns as is known in the art.Individual cells in the array 12 may be selected for a read or writeoperation by row decode circuitry 14 and column decode circuitry 16which operates in response to command information on a command bus 18and address information on an address bus 20. Signals appearing on thecommand bus 18 may include, but are not limited to, chip select, rowaddress strobe, column address strobe, write enable and clock enable.Sense amps 22 read information out of and write information into cellswhich have been selected by row decode circuitry 14 and column decodecircuitry 16 in response to read and write commands, respectively.

The sense amps 22 form part of a data path shown generally by referencenumeral 24. The data path 24 is the path along which data flows betweena data bus 26 and the array 12. For inbound data (data to be writteninto array 12), the data path begins at data pads 28 and ends with senseamps 22 writing the data into the array 12. For outbound data (data readfrom array 12), the path begins with the sense amps reading the datafrom the array 12 and ends with the data being output on the data pads28.

The data path 24 is comprised of a number of circuits for buffering andamplifying the data which are not shown as they do not form a part ofthe present invention. A plurality of output blocks 30 is arranged suchthat each output block 30 services one of the data pads 28. An exampleof a typical output block 30 is illustrated in FIG. 2. In FIG. 2, theoutput block 30 is comprised of a first plurality of enable transistors31, each connected in series with a drive transistor 32. The transistors31 each receive the data signal q, while each of the drive transistorsreceives one of the Vgate enable signal EnVg <0>, EnVg <1> . . . EnVg<6>. The output block is further comprised of a second plurality ofenable transistors 33, each connected in series with a drive transistor32. The first and second pluralities of enable transistors 31, 33,respectively, must be fully turned on by the signals q and q1 for thedrive transistors 32 to provide the proper pull-down load to the datapad 28 that it is servicing so that the voltage level necessary torepresent the data being transferred is quickly reached. Each of theother output blocks 30 may be identically constructed, and each receivesthe data signals q and q1 and Vgate enable signals EnVg <0> through <6>.

Each of the lines carrying the Vgate enable signals EnVg<0> through <6>is connected to a system voltage, V_(DD), through a p-channel transistor34. The gate of each of the transistors 34 is connected to a controlcircuit 36 through an inverter 38. The transistors 34 thus provide aplurality of switches which, under the control of control circuit 36,may momentarily connect the lines carrying the Vgate enable signals tothe voltage source V_(DD).

Completing the description of FIG. 1, a voltage regulator 40 providesthe voltage for the Vgate enable signals through Vgate enable control41. Vgate enable control 41 provides the Vgate enable signals to theoutput blocks 30 through a bus 42. The bus 42 is comprised of aplurality of lines each carrying one of the Vgate enable signals EnVg<0> through <6>.

Turning now to FIG. 3, a circuit diagram illustrating one implementationof the voltage regulator 40 constructed according to the presentinvention is illustrated. The voltage regulator 40 has an outputterminal 44. A p-channel transistor 46 is connected between a voltagesource and the output terminal 44 and an n-channel transistor 48 isconnected between the output terminal 44 and ground.

A transistor 50 receives at its gate terminal, through a pass gate 52,the same signal (OUT 1) that the transistor 46 receives. The pass gate52 is operative in response to a boost signal produced by the controlcircuit 36. The boost signal is also input to a gate terminal of ap-channel transistor 54 through an inverter 56. The p-channel transistor54 is connected across a gate terminal of the p-channel transistor 50and a voltage source.

In FIG. 4, a circuit diagram of a control circuit 36 which may be usedin conjunction with the voltage regulator of FIG. 3 is illustrated. InFIG. 4, a plurality of one-shot multivibrators 56 is provided. Each ofthe one-shots is triggered if its corresponding Vgate enable signal isenabled through Vgate enable control 41. An exemplary embodiment for oneof the one-shots 56 is illustrated at 56′. One-shot 56′ receives asignal <6> indicative of the need to enable the Vgate enable signal EnVg<6>. When the signal <6> indicates the need to enable the signal EnVg<6>, and an enable signal V-GCC_EN is present, the one-shot 56′ producesan output pulse 58. The output pulse 58 is input to the transistor 34through the inverter 38 shown in FIG. 1 to momentarily render thep-channel transistor 34 conductive. In that manner, the line carryingthe signal EnVg <6> is momentarily connected to the voltage sourceV_(DD), with the time of connection being determined by the width of thepulse 58. The other one-shots 56 are similarly constructed and used tomomentarily connect the other lines carrying the Vgate enable signals tothe voltage source V_(DD).

NOR gates 60, 61 and 62 are used to aggregate the pulses produced by theone-shots 56. The outputs of the NOR gates are input to a first logicgate 64 which is a NAND gate. The output of the NAND gate 64 isconnected to an input of a second gate which is a NOR gate 66. Theoutput of the NAND gate 64 is also connected to a second input of theNOR gate 66 through a delay circuit 68. The output of the delay circuit68 is connected to another input of the NOR gate 66 through a seconddelay circuit 70. The boost signal described above in conjunction withFIG. 3 is available at an output terminal of the NOR gate 66. Thatsignal may be delayed further by propagating it through a pair ofinverters 71 and 72.

The operation of the circuitry described thus far will now be explained.When the Vgate signal is loaded heavily as a result of variousconditions (e.g. during switching of the EnVg lines), the Vgate level atoutput terminal 44 in FIG. 3 may not recover sufficiently quickly. Twosteps are taken to boost the voltage. The first step is to render thep-channel transistor 34 servicing the relevant line carrying the Vgateenable signal which has just been enabled momentarily conductive throughuse of the pulse 58. That enables the individual line carrying theparticular Vgate enable signal to be momentarily connected to thevoltage source V_(DD). Thus, the plurality of transistors 34 may beconsidered to be part of a booster circuit as their function is tomomentarily boost the voltage available to the particular line carryingthe Vgate enable signal which has just been enabled.

The second step which is taken is described in conjunction with FIG. 3.When the boost signal goes active low, pass gate 52 becomes conductivewhich renders transistor 50 conductive which gives the voltage regulator40 much more pull-up capability. At the same time, transistor 54 isturned off. With the p-channel side of the regulator's output thusstrengthened, the voltage regulator 40 has about a 20 millivolt higherVgate regulation point. That helps Vgate hit its final value under heavyload conditions. Thus, the circuitry within the dotted box 74 may alsobe considered to be part of a booster circuit comprised of a transistor50 with the remaining components comprising a control circuit forcontrolling the conductivity of transistor 50.

If only the p-channel side of the voltage regulator 40 is strengthened,somewhat of an offset is created because the p-channel side of theoutput has more current carrying capability than the n-channel side.That offset can be compensated by adding a booster circuit 75 which issimilar to the circuit 74. In the booster circuit 75, the transistor 50becomes an n-channel transistor 50′. The control portion of the boostercircuit 75 is likewise changed as follows:

-   -   the transistor 54 becomes an n-channel transistor 54′. The        transistors 50′ and 54′ have their source and well connections        to V_(ss) and V_(bb), respectively. The input to pass gate 52′        is the same signal input to the gate of transistor 48.        Transistor 54′ receives the active low boost signal directly.        The sizing of the various components comprising the booster        circuit 75 would be such that the offset would be nulled out.

In summary, when selected Vgate enable signals are initially enabled,the booster circuit comprised of the plurality of transistors 34 isrendered operative so that one, some or all of the transistors 34 arerendered conductive to momentarily connect the line(s) carrying theVgate enable signal(s) to a voltage source. The boost signal, producedunder heavy load conditions, enables the output terminal 44 of thevoltage regulator 40 to be sourced with additional current throughbooster circuit 74 in an unbalanced mode, or through booster circuits 74and 75 in a balanced mode.

Production of the boost signal will now be described in conjunction withFIG. 4. In FIG. 4, the NAND gate 64 produces a control pulse whenever itreceives a low going pulse at one or more of its input terminals. TheNAND gate 64 will produce a control pulse whenever selected Vgate enablesignals are initially enabled. Optionally, the lowest three lines, lines2, 1 and 0 can be optioned out by a switch 76 because the capacitance onthose lines is so small that Vgate is not affected much when they turnon. Obviously, the selection of other types of gates and otherarrangements of gates could cause the control pulse to be produced underdifferent conditions.

It has been found that the control pulse produced by the NAND gate 64 isnot of sufficient duration. As a result, the control pulse is inputdirectly to the second gate 66 to cause the gate 66 to change states toa low state. The control pulse is also input to the gate 66 through thedelay circuit 68. In that manner, as the control pulse from gate 64prepares to end, a delayed control pulse produced by delay circuit 68becomes available at an input terminal of the gate 66, thereby insuringthat the output of the gate 66 does not change state. In a similarmanner, the delayed control pulse produced by the delay circuit 68 isinput to the second gate 66 through the delay circuit 70 such that whenthe delayed control pulse produced by the delay circuit 68 is preparingto end, the delayed control pulse produced by the delay circuit 70 isinput to an input terminal of the gate 66 thereby insuring that theoutput of the gate 66 does not change when the delay pulse produced bythe delay circuit 68 ends. By chaining together a plurality of delaycircuits 68 and 70, and producing a plurality of delayed control pulses,a control pulse of extended duration can be obtained at the output ofthe second gate 66. Additional delay circuits 68, 70 can be added toincrease the length of the control pulse of extended duration. Thecontrol pulse of extended duration is the boost signal which is input tothe control portion of the booster circuit 74.

The delay circuits 68 and 70 together with the NOR gate 66 may be viewedas a pulse extender. To insure glitch-free operation, the pulse extenderof the present invention should have outputs taken from enough pointsalong the delay line to insure no glitch in the extended pulse.

Returning to FIG. 3, the voltage regulator 40 may have a differentialamplifier 78 which produces a first output signal, OUT 1, for directlydriving transistor 46 and a second output signal, OUT 2, whichindirectly drives transistor 48. A bias voltage is supplied to thedifferential amplifier 78 through an n-channel transistor 82. Transistor82 is responsive to a control signal VgRegBias. A transistor 84 isconnected in series with a transistor 85, with the two transistors 84and 85 connected in parallel with the transistor 82. The boost signalmay be additionally used to control the transistor 84. Because the boostsignal is active low, an active high version is taken from the output ofinverter 56, such that when the boost signal is active, the transistor84 is turned on.

When going into nap or standby modes, the voltage regulator needs to goto a low power mode very quickly. It has been determined that the stepscurrently taken to reduce the bias voltage, by decreasing the controlsignal VgRegBias, are insufficient. As shown in FIG. 5, a one-shot 86 isresponsive to a signal VgNap which is responsible for putting thevoltage regulator 40 into a nap or standby mode. The one-shot 86produces an output pulse which temporarily renders transistor 88conductive. When the transistor 88 is conductive, a transistor 90,connected to operate as a diode, pulls the signal VgRegBias within a Vtof ground thereby causing it to decrease even more rapidly. When thesingle pulse produced by the one-shot 86 is no longer available, thediode 90 is no longer conductive as the transistor 88 is turned off. Inthat manner the reduction in bias voltage can be increased.

It has been determined that even if the voltage reduction of the signalVgRegBias occurs sufficiently quickly, a compensation resistor 92 andcompensation capacitor 94, which are a load across the transistor 46,can keep the p-channel transistor 46 from reducing its drivesufficiently quickly. The pulse produced by the one-shot 86 of FIG. 5 isused to pull a node 96 between the resistor 92 and capacitor 94 to apredefined voltage other than zero through a transistor 98. In theembodiment shown in FIG. 3, the predefined voltage is V_(DD) whichallows transistor 46 to go to a low power mode very quickly. Thisactually shuts off the transistor 46 briefly, but because that shutoffoccurs at the beginning of a nap or standby mode, the shutoff is anon-issue. To avoid that brief shutoff, instead of pulling the node 96up to V_(DD), the node 96 could be pulled up to a large p-channel diodetied to V_(DD). The p-channel diode must be sized such that it allowsquick pullup while leaving transistor 46 on near steady state nap orstandby conditions. That embodiment comes at a layout expense as thep-channel diode needs to be sufficiently large.

Illustrated in FIG. 6 is an output pre-driver circuit 100. Thepre-driver circuit 100 is constructed of a first data path 102responsive to a data signal q and a second data path 104 responsive to adelayed version of the data signal q′ which is delayed by less than180°. The first data path 102 has two output transistor drive stages 106and 108 while the second data path 104 similarly has two transistoroutput drive stages 110 and 112. The transistors 106 and 110 are enabledwhen a signal s11 renders a transistor 114 conductive. The transistors108 and 112 are operative when a signal s12 renders a transistor 116conductive.

It is known in the art to monitor the strength of the p-channel andn-channel transistors in an output drive device (not shown) and togenerate a two-bit signal where s11 and s12 represent the two bits ofthe binary signal. The implementation of the output pre-driver 100 inFIG. 6 allows the p-channel device 106 to be rendered conductiveindependently of the p-channel device 108. The p-channel device 110 canbe enabled independently of the p-channel transistor 112. As a result,all four transistors 106, 108, 110 and 112 may be on, transistors 106and 110 may be on while transistors 108 and 112 may be off, andtransistors 108 and 112 may be on while transistors 106 and 110 are off.With the arrangement shown in FIG. 6, three of the four two-bit codescan have different total amounts of p-channel drive enabled in thepre-driver 100. With proper tuning, more skew can be eliminated from thesubsequent output driver stages with the pre-driver 100 illustrated inFIG. 6.

FIG. 7 illustrates a computer system 200 containing the memory ofFIG. 1. The computer system 200 includes a processor 202 for performingvarious computing functions, such as executing specific software toperform specific calculations or tasks. The processor 202 includes aprocessor bus 204 that normally includes an address bus, a control bus,and a data bus. In addition, the computer system 200 includes one ormore input devices 214, such as a keyboard or a mouse, coupled to theprocessor 202 to allow an operator to interface with the computer system200. Typically, the computer system 200 also includes one or more outputdevices 216 coupled to the processor 202, such output devices typicallybeing a printer or a video terminal. One or more data storage devices218 are also typically coupled to the processor 202 to allow theprocessor 202 to store data in or retrieve data from internal orexternal storage media (not shown). Examples of typical storage devices218 include hard and floppy disks, tape cassettes, and compact diskread-only memories (CD-ROMs). The processor 202 is also typicallycoupled to cache memory 226, which is usually static random accessmemory (“SRAM”) and to an SDRAM 228 through a memory controller 230. Thememory controller 230 normally includes a control bus 236 and an addressbus 238 that may be coupled to the SDRAM 228. A data bus 240 may becoupled to the processor bus 204 either directly (as shown), through thememory controller 230, or by some other means.

While the present invention has been described in conjunction withpreferred embodiments thereof, those of ordinary skill in the art willrecognize that many modifications and variations may be made. Theforegoing description and the following claims are intended to cover allsuch modifications and variations.

1. A pre-driver having an unbalanced output, comprising: a first datapath for carrying a data signal, said first data path having a pluralityof transistor output stages; a second data path for carrying a datasignal that is a delayed version of said data signal carried by saidfirst data path which is delayed by less than 180°, said second datapath having a plurality of transistor output stages; and a plurality ofswitches, each switch for controlling the conductivity of a pair of saidplurality of transistor output stages in response to the level ofconductivity of a subsequent driver output stage, wherein one of saidpair of transistor output stages is connected to said first data pathand another of said pair of transistor output stages is connected tosaid second data path.
 2. A method of providing an unbalanced outputdrive capability to correct for output skews in subsequent amplificationstages, comprising: carrying a data signal on a first data pathcomprised of a plurality of output drive stages; carrying a delayedversion of said data signal which is delayed by less than 180° on asecond data path comprised of a plurality of output drive stages;controlling in pairs the number of output drive stages on said first andsecond data paths that are activated in response to the amount of skew,said output stages including at least one pair of output drive stageswherein one output transistor of said pair is connected to said firstdata path and another of said pair of output transistors is connected tosaid second data path.
 3. The method of claim 2 wherein said step ofcontrolling includes the step of generating a two-bit code and whereinsaid two-bit code is used to control the number of active output drivestages.
 4. A method of providing an unbalanced output drive capability,comprising: generating a two-bit signal representative of the relativestrength of an n-channel transistor and a p-channel transistor in anoutput device; and controlling the number of output pre-driver stagesthat are active on a first data path for carrying a data signal andcontrolling the number of output pre-driver stages that are active on asecond data path for carrying a delayed version of said data signalwhich is delayed by less than 180° in response to said two-bit signal,wherein at least a first pair of said output stages is controlled by thefirst bit of said two-bit signal and at least a second pair of saidoutput stages is controlled by the second bit of said two-bit signal,and wherein one output stage of each of said pairs is connected to saidfirst data path and another output stage of each of said pairs isconnected to said second data path.
 5. A method, comprising: generatinga signal representative of the relative strength of an n-channeltransistor and a p-channel transistor in an output device; enablingcertain output stages in a pre-driver in response to said signal,wherein said pre-driver includes a first data path for carrying a datasignal and a second data path for carrying a delayed version of saiddata signal which is delayed by less than 180°, wherein said pre-driverproduces an unbalanced output, and wherein at least a pair of saidcertain output stages is enabled in response to said signal, said pairhaving an output stage connected to said first data path and anotheroutput stage connected to said second data path; and inputting a datasignal to the output device through the pre-driver.
 6. A pre-driverproviding an unbalanced output drive capability, comprising: a firstdata path for carrying a data signal, said first data path having aplurality of output transistors; a second data path for carrying adelayed version of said data signal which is delayed by less than 180°,said second data path having a plurality of output transistors; and aplurality of switches, each switch for controlling the conductivity of apair of said plurality of output transistors in response to signalsindicative of the strength of the output transistors in an outputdevice, wherein one of said pair of output transistors is connected tosaid first data path and another of said pair of output transistors isconnected to said second data path.
 7. A portion of a data path,comprising: an output driver responsive to a data signal; and apre-driver providing an unbalanced output drive capability, comprising:a first pre-driver data path for carrying a data signal, said firstpre-driver path having a plurality of output transistors; a secondpre-driver data path for carrying a delayed version of said signal whichis delayed by less than 180°, said second pre-driver path having aplurality of output transistors; and a plurality of switches, eachswitch for controlling the conductivity of a pair of said plurality ofoutput transistors in response to signals indicative of the strength ofoutput transistors in said output driver wherein one of said pair ofoutput transistors is connected to said first pre-driver data path andanother of said pair of output transistors is connected to said secondpre-driver data path, said pre-driver for providing said data signal tosaid output driver.
 8. A memory device, comprising: a plurality ofmemory cells arranged in an array of rows and columns; a plurality ofdevices for identifying cells within said array; a plurality of pads; adata path connecting said plurality of pads and said array, said datapath comprising: an output driver responsive to a data signal; and apre-driver providing an unbalanced output drive capability, comprising:a first pre-driver data path for carrying a data signal, said firstpre-driver path having a plurality of output transistors; a secondpre-driver data path for carrying a delayed version of said data signalwhich is delayed by less than 180°, said second pre-driver path having aplurality of output transistors; and a plurality of switches, eachswitch for controlling the conductivity of a pair of said plurality ofoutput transistors in response to signals indicative of the strength ofoutput transistors in said output driver wherein one of said pair ofoutput transistors is connected to said first pre-driver data path andanother of said pair of output transistors is connected to said secondpre-driver data path, said pre-driver for providing said data signal tosaid output driver.
 9. A computer system, comprising: a processor havinga processor bus; an input device coupled to the processor through theprocessor bus; an output device coupled to the processor through theprocessor bus; a memory device coupled to the processor bus, said memorydevice comprising: a plurality of memory cells arranged in an array ofrows and columns; a plurality of devices for identifying cells withinsaid array; a plurality of pads; a data path connecting said pluralityof pads and said array, said data path including: an output driverresponsive to a data signal; and a pre-driver providing an unbalancedoutput drive capability, comprising: a first pre-driver data path forcarrying a data signal, said first pre-driver path having a plurality ofoutput transistors; a second pre-driver data path for carrying a delayedversion of said data signal which is delayed by less than 180, saidsecond pre-driver path having a plurality of output transistors; and aplurality of switches, each switch for controlling the conductivity of apair of said plurality of output transistors in response to signalsindicative of the strength of output transistors in said output driverwherein one of said pair of output transistors is connected to saidfirst pre-driver data path and another of said pair of outputtransistors is connected to said second pre-driver data path, saidpre-driver for providing said data signal to said output driver.